Masato Ito

Catalytic Hydrogenation of Carboxamides and Esters by Well-Defined Cp*Ru Complexes Bearing a Protic Amine Ligand

A novel catalytic method for the straightforward hydrogenation of carboxamides and esters to primary alcohols has been developed. Chiral modification in the ligand sphere of the well-defined Cp*Ru catalyst molecule opens up a new possibility for the development of an enantioselective hydrogenation of racemic substrates via dynamic kinetic resolution.

Highly Enantioselective Hydrogenative Desymmetrization of Bicyclic Imides Leading to Multiply Functionalized Chiral Cyclic Compounds

Highly enantioselective hydrogenative desymmetrization of bicyclic imides has been developed with chiral Cp*Ru(PN) catalysts. The present hydrogenation directly provides stereochemically well-defined cyclic compounds with excellent enantiomeric exessses, which might otherwise require a detour to reach.

Insulated Molecular Wires: Dendritic Encapsulation of Poly(triacetylene) Oligomers, Attempted Dendritic Stabilization of Novel Poly(pentaacetylene) Oligomers, and an Organometallic Approach to Dendritic Rods

Multinanometer-long end-capped poly(triacetylene) (PTA) and poly(pentaacetylene) (PPA) oligomers with dendritic side chains were synthesized as insulated molecular wires. PTA Oligomers with laterally appended Frechet-type dendrons of first to third generation were prepared by attaching the dendrons (8, 13, and 17, respectively, Scheme 1) to (E)-enediyne 18 by a Mitsunobu reaction and subsequent Glaser-Hay oligomerization under end-capping conditions (Scheme 2). Whereas first-generation oligomers up to the pentamer were isolated (1a – e), for reasons of steric overcrowding, only oligomers up to the trimer (2a – c) were formed at the second-generation level, and only the end-capped monomer and dimer (3a, b) were isolated at the third-generation level. By repetitive sequences of hydrosilylation (with the Karstedt catalyst), followed by allylation or vinylation, a series of carbosilane dendrons were also prepared (Schemes 3 and 4). Attachment of the second-generation wedge 40 to (E)-enediyne 18, followed by deprotection and subsequent end-capping Hay oligomerization, provided PTA oligomers 4a – d with lateral carbosilane dendrons (Scheme 5). UV/VIS Studies (Figs. 5 – 10) demonstrated that the insulating dendritic layers did not alter the electronic characteristics of the PTA backbone, even at the higher-generation levels. Despite distortion from planarity due to the bulky dendritic wedges, no loss of π-electron conjugation along the PTA backbone was detected. A surprising (E)(Z) isomerization of the diethynylethene (DEE) core in the third generation derivative 3a was observed, possibly photosensitized by the bulky Frechet-type dendritic wedge. Electrochemical investigations by steady-state voltammetry and cyclic voltammetry showed that the first reduction potential of the PTA oligomer with Frechet-type dendrons is shifted to more negative values as the dendritic coverage increases. With compounds 5a – c, the first oligomers with a poly(pentaacetylene) backbone were obtained by oxidative Hay oligomerization under end-capping conditions (Scheme 6). The synthesis of dendritic PPA oligomers by oxidative coupling of (E)-enetetrayne 60 under end-capping conditions provided oligomers 61a – d, which were formed as mixtures of stereoisomers due to unexpected thermal (E)(Z) isomerization (Scheme 8). In another novel approach towards dendritic encapsulation of molecular wires with a Pt-bridged tetraethynylethene (TEE) oligomeric backbone, the trans-dichloroplatinum(II) complex trans-67 with dendritic phosphane ligands (Fig. 14) was coupled under Hagihara conditions to mono-deprotected 69 under formation of the extended monomer 65 (Scheme 12). Again, an unexpected thermal (E)(Z) isomerization, possibly induced by steric strain between TEE moieties and dendritic phosphane ligands in the unstable complex, led to the isolation of 65 as an isomeric mixture only.

Dendritic rods with a poly(triacetylene) backbone: insulated molecular wires

Multinanometer long phenylacetylene-end-capped poly(triacetylene) (PTA) oligomers with dendritic side chains of generation one to three have been prepared; UV–VIS measurements indicate that there is no loss of π-electron conjugation along the PTA backbone in the higher generation compounds despite distortion from planarity due to the bulky dendritic wedges.

Catalytic Enantioselective Synthesis of Planar-Chiral Cyclic Amides Based on a Pd-Catalyzed Asymmetric Allylic Substitution Reaction

The highly enantioselective synthesis of planar-chiral nine-membered cyclic amides was achieved by the Pd-catalyzed asymmetric allylic cyclization of achiral linear precursors in the presence of a catalytic amount of chiral ligand.

Hydrogenation of polar functionalities with Cp*Ru(PN) catalysts

This account deals with an overview of our recent progress toward the development of molecular catalysts for the reduction in polar functionalities with molecular hydrogen (H2). An emphasis is placed on the newly designed Cp*Ru(PN) complexes, which have been identified as efficient catalysts for the hydrogenation of imides. The structural modification of the complex enhances the catalytic performance and allows efficient access to various chiral synthetic intermediates.

The moment lever arm is a predictor of the pronation in running

The over-pronation of foot in the running stance phase is a major factor of running injury. Therefore, running shoes need feature to prevent over–pronation in stance phase. Many earlier studies about foot pronation focused on kinematic parameters such as pronation angles (Nigg 1999). Going through biomechanical predictor is necessary in designing pronation control shoes. Basically pronation is occurred as the results of such forces acting at foot caused by the ground reaction force (GRF) etc. Therefore, in this study, the moment produced by GRF around the ankle joint center is calculated from experimental results and it is discussed how the factors of the moment can affect.

Control of the degree of molecular recognition by shape-specific weak interactions between nonpolar groups

In oxidation of a pair of associating thiols [(1) and (2)], each having a phenyl or a hexyl group (R = n-C6H13, i-C6H13, cyclo-C6H11), it has been shown that the order of the selectivity [a measure of the degree of the recognition between (1) and (2)] for R (i.e.,n-C6H13-C6H13 >cyclo-C6H11) depends upon the strength of the phenyl–R interactions.

Marked effect of the shape of solvent molecules on molecular recognition in the oxidation of associating thiols

Oxidation of a pair of associating thiols (1 and 2), each having a binding site [–C(O)NHC(O)NH–] and a recognition site (R1 or R2), is examined in binary solvent mixtures of a propanol with water and organic co-solvents. The selectivity (r)—a measure of the degree of recognition of (1) by (2)[or of (2) by (1)]—in the oxidation is represented by the logarithmic ratio of the yield of an unsymmetrical disulphide to twice that of a symmetrical one. It is found that (i) higher selectivity is achieved when the non-polar group of a propanol in a mixed solvent resembles a given non-polar group of one of the reacting molecules in three-dimensional shape and (ii) the above ‘solvent shape effect’ on the selectivity is produced more markedly in aqueous propanols than in the corresponding non-aqueous ones. Correlation of the observed selectivity with physico-chemical properties of (aqueous) propanols, reactivity difference between thiols, and so on is discussed together with a possible explanation of the solvent shape effect on the degree of recognition of non-polar groups.

Shape similarity effect on the strength of weak interactions of a phenyl group with unsaturated hydrocarbons and ethers

Gas chromatographic studies for pairs of six-membered-ring(cyclic) and straight-chain hydrocarbons and ethers have shown that the weak interactions of the phenyl group in a stationary liquid are more attractive with the cyclic hydrocarbons and ethers, which are similar in shape to the phenyl group, than with the straight-chain hydrocarbons and ethers, each pair containing the same number of π-electrons or oxygen atoms.